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The cognitive and neural basis of the 'Real Object Advantage’ in shape recognition
AuthorHoller, Desiree E
AdvisorSnow, Jacqueline C
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In scientific research, artificial stimuli, such as images presented on a computer screen, are thought to be adequate replacements for real objects to understand the cognitive and neural basis of object perception in humans. However, real objects differ from pictures in many respects, including the fact that they offer the potential for action (whereas images do not). Accordingly, there is increasing scientific evidence that real objects elicit responses that are different than those elicited by pictures or computerized images, although the underlying cause of these differences is largely unknown. In particular, some of my earlier research revealed a surprising phenomenon known as the ‘Real-Object Advantage’ in neuropsychological patients with visual agnosia. These patients, who have damage to object-processing areas in the ventral visual pathway of the brain, are classically unable to recognize pictures of objects. However, I found that these patients show a surprising sparing in their ability to recognize real-world solid objects, although the effect is only apparent when the objects are presented in their familiar real-world size (but not when size is altered so that the objects appear smaller or larger than the expected real-world-size). In this Ph.D. thesis, I investigated the generalizability of the Real Object Advantage by studying object recognition in neurologically healthy observers. In Aim 1, I show that healthy observers, like patients, show a Real Object Advantage in recognition and that the effect is modulated by expectations about an object’s real-world size. In Aim 2, I investigated the neural basis of the effect using functional magnetic resonance imaging (fMRI). I explored whether there are differences in how real objects and pictures are processed in the ventral (‘perception’) and dorsal (‘action’) visual processing pathways in healthy adults. To do this, I developed innovative new techniques and apparatus to present real-world objects in high-field MRI environments. I found that although real objects and pictures elicit responses that are similar at the large-scale, real objects nevertheless elicited shape-selective responses that were more unique from one observer to the next, and that were maximal in more anterior brain areas, compared to pictures or images of objects. Taken together, the findings demonstrate that the Real Object Advantage is a generalizable effect, in which real objects are more easily recognized, and are processed differently, than artificial stimuli. The effect is not attributable to differences between real objects and pictures in three-dimensional depth cues, but rather, because of differences in higher-level attributes such as multisensory characteristics and relevance for action. The research provides important new insights into the cognitive and neural basis of vision in naturalistic environments, and it highlights how ecologically-valid stimuli are important for understanding the integrated workings of the perception and action systems.